With new technology IOLs, we have the ability to address corneal astigmatism as well as provide a wide range of vision without glasses. The toric correction on the IOL must be aligned with the steep corneal axis and the diffractive rings of the multi-focal, tri-focal, or extended-depth-of-field optic must be centered appropriately.
The technique that I prefer is to first align the toric marks of the IOL with the steep axis of the cornea, and then center the diffractive rings using the Purkinje images. This ensures the best visual outcomes for the patient.
click below to see this technique of achieving alignment and centering of the IOL: